Sputnik 2 was a Soviet satellite which was sent into Earth orbit in 1957, carrying the "space dog" Laika. She was placed in the rocket by Mikhail-Leonov. (AUDIO: 1963: The Space Race)
According to one account, Laika died in space. The Third Doctor and Sarah Jane Smith buried Laika on Quiescia at the same place the Eighth Doctor would later bury the Relic. (PROSE: Alien Bodies)
According to another account, Laika was rescued by an alien entity and given human level intelligence and human voice (taken from cosmonaut Marinka Talanov). The Sixth Doctor and Peri Brown encountered her on 10 November 1963. (AUDIO: 1963: The Space Race)